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In the US, I was taught that you use and when there's a decimal: 13.5 = "thirteen and a half" or 1.3 = "one and a third" or 1,345.257 = "one thousand three-hundred forty-five and two-hundred fifty-seven thousandths".
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Roddy of the Frozen PeasOct 3 '12 at 0:29

"Three hundred and forty two" is what people say in Britain, Australia and New Zealand. The OED has examples demonstrating this, so I don't know why anyone would assert that this is not correct. Maybe tchrists's comment above should be amended to read in no country called the United States of America is "three hundred and forty two" ever correct.
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user16269Oct 3 '12 at 4:39

1

@David: I think tchrist means it is incorrect to omit the hyphen in 'forty-two'.
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GEdgarOct 3 '12 at 15:06

Three hundred forty-two for American English. I always have to delete the and in Taiwanese Chinese-English, & I often have to add the hyphen between forty and two. Historically, of course, many Americans wanted to be different: specifically, they wanted to be independent & sovereign rather than ruled by the king of England. But almost all the differences between the Anglophone countries evolved for a variety of reasons that have little or nothing to do with a narcissistic desire to be unique or even very unique. But ethnocentrism's a normal human bias & not worth a temper tantrum.
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user21497Oct 3 '12 at 3:42

To my ear, "and" would not sound correct with a voiced "d", nor following a voice "d" on "hundred" or "thousand", but when more numbers follow "hundred" the "d" is stifled such that it sounds a bit like "nd".
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supercatMay 1 '14 at 15:57